getting the dual variables

[juan raposo]

Hi,

I'm currently working on a mixed integer linear program in which I have binary and NonNegativeReal variables. Is it possible to obtain its dual variables? I am asking this because  when I try to get some specific dual variable associated to a constraint, I get an error message such as: 

 KeyError: "Component with id '1595808824672': Lower_W[HYDRO_RES,1]"

And when using instance.dual.display() I get the following message:

   dual : Direction=Suffix.IMPORT_EXPORT, Datatype=None Key : Value

Also the motive of this question is because I ve seen the following discussion at StackOverflow:

https://stackoverflow.com/questions/64160458/dual-variable-returns-nothing-in-pyomo

Could someone confirm if this is true? 

In case it is not, I am sharing my code of my GitHub repository:

https://github.com/juanraposo2000/PYOMO/blob/main/MMP_PYOMO.ipynb

  

[David Woodruff]

The statement on the stack overflow page you cited (that you can't get duals for a problem with integer variables) is true enough for your purposes.

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